Surge suppressor for fluid lines

ABSTRACT

A surge suppressor for use with outlet conduits of pumps, such as air-operated diaphragm pumps, having a pulsating output and other fluid conduits that are subject to surges or shock pressures. The apparatus embodies a diaphragm, one side of which is subjected to the pressure of the fluid in the conduit and the other side of which is subjected to the pressure of air within a chamber. Means are provided for automatically compensating for changes in the fluid pressure in the conduit by supplying air to the chamber if the pressure in the conduit increases and automatically bleeding air from the chamber if the pressure decreases, thus maintaining a substantially constant volume of air in the chamber even though the pressure in the conduit to which the device is attached may vary.

o v United States Patent [1 1 1 9 9 upp Y June 26, 1973 [5 SURGESUPPRESSOR FOR FLUID LINES 1,014,357 12/1965 Great Britain 417/540 7-1tzW E. M fld,0h men or Rupp ans 1e 10 Primary Examiner-William L. Freeh[7 3] Assignee: TheWan-en R pp Company, Assistant Examiner-Leonard SmithMansfield, Ohio Attorney-Bosworth, Sessions, l-lerrstrom & Cain [22]Filed: Dec. 17, 1970 21 A l N 99 078 [57] ABSTRACT 1 pp A surgesuppressor for use with outlet conduits of pumps, such as air-operateddiaphragm pumps, having [52] US. Cl. 417/540, 130/31 a pul ating outputand other fluid conduits that are sub- [51] Int. Cl. F04b 11/00, F16155/04 ject to surges or shock pressures. The apparatus em- 1 F 181d 01Search bodies a diaphragm, one side of which is subjected to 417/540,541, 5 the pressure of the fluid in the conduit and the other side ofwhich is subjected to the pressure of air within References Cited achamber. Means are proyided for automatically com- UNITED STATES PATENTSpensating for changes in the fluid pressure in the con- 3 692 433 911972Finger 417/395 x duit by supplying chambe if the P'essme in 1 2/1957'417/395 the conduit increases and automatically bleeding air 3,299,8261/1967 417/395 from the chamber if the pressure decreases, thus main-$391,963 7/1968 417/395 X taining a substantially constant volume of airin the 3,514,227 5/1970 Rup 417/395 chamber even though the pressure inthe conduit to which the device 15 attached may vary.

636,762 2/1962 Canada 417/543 113 Claims, 5 Drawing Figures PATENIEDmzsms 3.741.692

SHEEIINZ INVENTOR. a9 30 weer/d 6. IPUPP M, yin/147% 4) SURGE SUPPRESSORFOR FLUID LINES BACKGROUND OF THE INVENTION This invention relates to asurge suppressor or pulsation absorber for use in conjunction withconduits or piping carrying fluids and which are subject to pressuresurges or pulsations resulting, for example, from a pump having apulsating output or from water hammer or shock pressures caused by rapidclosings of valves and the like. The inventionrelates particularly to adiaphragm type of surge suppressor and to the combination of such asurge suppressor with an air-operated diaphragm type of pump with whichthe suppressor is particularly effective.

Air-operated diaphragm pumps are widely used, particularly for pumpingliquids, solutions, viscous materials and slurries or suspensionscontaining substantial amounts of solids (the word liquid" as usedherein is intended to include all such material) which may be abrasive.Air-operated diaphragm pumps have a pulsating output and it is desirableto employ pulsation absorbers or surge suppressors in their dischargelines.

Air chambers have long been used as surge suppressors in liquid systems.These simply provide a chamber for air with the bottom of the chamberopen to contact with the liquid in the system. Liquid flows into thechamber and the air in the chamber is compressed upon the occurrence ofa pulse of increased pressure in the system and the air expands andreturns the liquid to the system after the pulse has passed. It has alsobeen proposed to separate the liquid being pumped from the 'air in thechamber by a diaphragm, bladder or the like to prevent the air fromdissolving in the liquid. However, these devices are subjecttodifficulties for the reason that if the pressure changes in the pipingsystem to which the suppressor is attached, the volume of air above theliquid also changes. At a higher than usual liquid pressure there mightbe a very small volume of air in the chamber and if a further surgeshould take place the pressure in the chamber would build up rapidly andthe smoothing action of the chamber would be diminished. Also, in surgesuppressors of the type embodying a movable dividing member such as adiaphragm or piston between the air and the liquid in the system, themovement of the dividing member is usually limited and if the pressureof air on the dividing member is too high or too low as compared to thepressure of the liquid, then the dividing member may remain at one endof its stroke or the other and the device will be ineffective as a surgesuppressor.

SUMMARY OF THE INVENTION A general object of the present invention is toprovide an improved surge suppressor for liquid piping sys tems in whichthe difficulties with previously known types of surge suppressors arelargely eliminated. Another'object of the invention is to provide adiaphragm type surge suppressor that is particularly adapted for use incombination with an air-operated diaphragm pump. Another object is toprovide a pumping system embodying an air-operated diaphragm pump and adiaphragm type surge suppressor that will produce an output in which thepulsations are greatly reduced as compared to the pulsations in theoutput of the pump alone.

Briefly, these and other objects of the invention are attained byproviding a surge suppressor comprising a closed chamber containing agas (ordinarily air) under pressure and having at one end of the chambera dividing member which preferably takes the form of a flexiblediaphragm, but which can be a piston or the like, one side of which isexposed to the gas pressure in the chamber and the other side of whichis exposed to the pressure of the liquid in the conduit with which thedevice is associated. The chamber is provided with an inlet valveconnected to a conduit for supplying gas under pressure and an outletvalve through which gas under pressure can be bled from the chamber.These valves are operated by the dividing member in such manner that ifthe pressure of the liquid in the conduit is such that the dividingmember approaches the limit of its movement into the chamber, the inletvalve is opened momentarily to admit gas under pressure into the chamberwhile if the dividing member approaches the limit of its stroke inmomentarily to opposite direction, the outlet valve is openedmomentarilyto permit the discharge of gas from the chamber. By thismeans, the volume of gas within the chamber is maintained substantiallyconstant regardless of changes in pressure of the liquid and thedividing member moves approximately equal distances in both directionsfrom its mid position. Thus, the device operates efficiently andeffectively to absorb pulsations and surges regardless of reasonablevariations in the pressure in the liquid in the system, and in the caseof a device in which the dividing member takes the form of a diaphragm,the diaphragm is not unduly strained in either direction. A systemembodying in combination an air-operated diaphragm pump and a diaphragmtype surge suppressor is particularly effective and economical inasmuchas the air supply that is used to operate the pump can also be employedto furnish air to the gas chamber of the suppressor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofa surge suppressor made according to a preferred form of the invention.

FIG. 2 illustrates a system comprising a surge suppressor made accordingto the invention in combination with an air-operated diaphragm pump of aknown type, parts of the pump being broken away for purposes ofillustration.

FIG. 3 is a vertical axial sectional view of a preferred form of airinlet valve used in the surge suppressor.

FIG. 4 is a similar view of a preferred form of air outlet valve used inthe surge suppressor; and

FIG. 5 is a transverse section as indicated by the line 5-5 of FIG. 3.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIG. 1 of the drawing,a surge suppressor 9 made according to a preferred form of my inventioncomprises an air or other gas chamber 10 within an air chamber housing11, and a liquid chamber 12 within a liquid chamber housing 13. Thehousings 1 1 and 13 are ordinarily in the form of metal castings andcircular in cross section. At the bottom of the air chamber housing 11there is an annular flange l4 and a similar-flange 15 is formed at thetop of the liquid chamber housing 13. A flexible diaphragm 16 of knownconstruction is clamped between the opposing surfaces of the two flangesand the two housings are secured together by a conventional V-clamp 17.The diaphragm 16 thus separates the air chamber 10 from the liquidchamber 12 so the diaphragm is subjected on one side to the pressurewithin the air chamber and on the other side to the pressure of theliquid within the liquid chamber 12.

The lower part of the housing 11 and the upper part of the housing 13define between them a diaphragm chamber 19. The housing 11 extendsinwardly and upwardly from the flange 14 to provide a generally conoidalsurface 20 which terminates in an inwardly extending flange 21 having acircular opening 22 therein that provides communication between thediaphragm chamber 19 and the air chamber 10. Similarly, the housing 13extends inwardly and downwardly from the flange to provide a generallyconoidal surface 24 of about the same extent as the surface 20. Thesurface 24 merges into a sloping surface 25 that terminates in a boss 26having an internally threaded opening 27 that receives a fitting 28.Fitting 28 in turn is connected to a T-fitting 29 that is inserted intoa pipe or conduit 30 which may be the discharge conduit that issubjected to pulsations or surges. The under side of diaphragm 16 issubjected to the pressure of the liquid in the conduit 30 while theupper side of the diaphram is subjected to the pressure of the gas inthe chamber 10.

The displacement of the diaphragm from its mid position is limited inthe upward direction by the surface and in the lower direction by thesurface 24. Also, the central portion of the diaphragm is supported bycircular plates 32 and 33 that are clamped against the diaphragm by nuts34 threaded on a rod 35 which, as described below, is employed tooperate the valves for controlling the volume of air or other gas in thechamber 10. The plates 32 and 33 are provided with peripheral flanges 36and 37 that engage the internal flange 21 of the housing 11 and thesurface of the housing 13, respectively, to limit positively the extremedisplacement of the diaphragm in either direction and thus inconjunction with the surfaces 20 and 24 to prevent the diaphragm frombeing subjected to unduly large displacement. Normally, as explainedbelow, the maximum stroke of the diaphragm is from a lower positionapproximately as shown in full lines in FIG. 1 to an upper position asshown approximately in broken lines in FIG. 1. i

In order to provide an air chamber having a volume several times thevolume displaced by the diaphragm in its normal full stroke, the airchamber housing 11 is enlarged in diameter above the flange 21 to adiameter about equal to the diameter of the diaphragm and extendsupwardly a distance sufficient to give the desired volume. An airchamber of substantial volume is important to minimize the changes inpressure within the chamber as the diaphragm reciprocates through acomplete stroke. By this mode of operation the deviations in pressure inthe line from the mean pressure output are minimized.

It will be evident that in the operation of the surgesupppressor thesurge suppressor within the air chamber should be substantially equal tothe pressure in the liquid conduit 30. In prior types of surgesuppressors, such as the old and well known air chamber, this isaccomplished automatically by simply permitting the liquid being pumpedto compress the air in the air chamber so that the liquid occupies agreater proportion of the volume of the chamber as the pressureincreases and if the pressure in the liquid decreases the air in thechamber expands and some of the liquid is returned from the air chamberto the liquid system. This same action takes place in surge suppressorsin which a very thin bladder or diaphragm is employed to separate theliquid being pumped from the gas. The use of a bladder or diaphragmeliminates the difficulties that arise with simple air chambers becauseof the reduction in volume of air resulting from the dissolution of theair in the chamber in the liquid being pumped. Both types of devices,however, are subject to a serious defect in that as the pressure of theliquid being pumped increases, the volume of air in the chamberdecreases. A substantial build up in pressure in the air chamber thentakes place with each pulse because of the comparatively small volume ofair and this buildup prevents devices of this type from effectivelyabsorbing pulsations under varying conditions of operation.

According to the present invention, these difficulties are eliminated byautomatically adding air to or bleeding air from the air chamber so asto maintain the volume of air within the chamber substantially constantregardless of changes in pressure in the fluid being pumped within thenormal range of operating pressures. This is preferably accomplished byproviding at the upper part of the air chamber 10 an air inlet valve 38connected to a source of air under pressure by a conduit 39, and an airoutlet or bleed valve 40 that discharges air from the chamber toatmosphere. The valves 38 and 40 are threaded into suitable openings ina closure member 41 that is secured to the necked-in upper portion 42 ofthe housing 11, an appropriate gasket 43 being employed to provide aleak proof joint.

In order to operate the valves 38 and 40 so as to maintain the volume ofair within the chamber 11 substantially constant, the valves areprovided with operating plungers or valve stems 45 and 46, respectively,which open the valves when they are moved inwardly with respect to thevalve bodies, the valves being closed and the stems returned by springsas described below.

The valves are automatically opened at the required times by theactuating rod 35. Rod 35 is made in two parts, a lower part 35a that issecured to the diaphragm l6 and an extension 35b that extends through anopening in a boss 48 in closure 41. The extension is slidably supportedby a bearing sleeve 49 disposed in the boss and a lip type seal 50prevents leakage of air from the chamber. A circular inlet valveoperating plate 51 is clamped between the upper end of the lower portion350 and the lower end of the extension 35b, extension 35b being threadedinto lower portion 35a as shown. A circular outlet valve operating plate52 is secured to the upper end of the extension as by a nut 53. Thelocation of the plates 51 and 52 on the rod 35 is such that the plate 52engages the valve stem 46 of the outlet valve and opens the valve whenthe diaphragm reaches approximately the position shown in full lines inFIG. 1, which is a short distance before the diaphragm reaches thedownward limit of its stroke. Similarly, the plate 51 engages the valvestem 45 to move it upwardly into the body of the valve 38 and open thevalve 38 when the diaphragm reaches approximately the dotted lineposition shown in FIG. 1, which is a short distance before the diaphragmreaches the upper limit of its stroke. The valves automatically closewhen the plates 51 and 52 are moved away from them by the operation ofthe diaphragm.

In operation, if the pressure in the conduit 30 becomes great enoughduring a surge or 'pulse or otherwise to move the diaphragm upwardlybeyond its normal maximum stroke, shown by the dotted lines position inFIG. 1, the valve 38 is opened momentarily to admit air from thecompressed air line39. On the other hand, if the pressure in the airchamber exceeds the liquid pressure so that the diaphragm goesdownwardly beyond its normal stroke as shown in full lines in FIG. 1,then the plate 52 depressesthe plunger 46 and opens the valve 40 tomomentarily bleed air out of the chamber 10. This happens repetitivelyunder either condition until a proper balance of pressure is restored.By this means, the pressure of the air within the chamber is varied inaccordance with the pressure of the pulsating liquid to maintain thevolume of air within the air chamber 10 substantially constant eventhough the pressure in the product being pumped through the line 30varies within normal operating limits. This assures effective operationof the surge suppressor with the diaphragm operating in the mid portionof its stroke and prevents the diaphragm from being subjected to unduestress.

While valves of any convenient type can be employed, I prefer to usevalves of the type shown in FIGS. 3 and 4. As shown in FIG. 3 the inletvalve 38 has a body 55 with a tapered pipe thread 56 that is threadedinto an aperture in the closure member 41. The valve has a cylindricalbore 57 that terminates in a conical valve seat 58 leading to a port 59.A poppet valve member 60 is disposed in the bore 57. This has ahexagonal body portion 61 that guides the valve in the bore and aconical portion 62 that conforms to the conical seat 58 and is providedwith a groove to receive an O-ring 63. The valve member terminates inthe valve stem 45. The valve member is urged toward the valve seat 58 bya spring 64 that acts between the end of the valve member 60 and aninlet fitting 66 that is threaded into the top of the valve body 55 andforms a connection with the air supply conduit 39. The flats on thehexagonal portion 61 of the valve member provide passages for the flowof air when the valve is opened and there is clearance around the stem45 to permit air to flow through the port 59 into the air chamber 11.When the stem 45 is contacted by the operating plate 51, the valvemember is lifted from its seat 58, disengaging the O-ring 63 from theconical surface 58 and admitting air from the conduit 39 through thefitting 66 and the valve body and into the air chamber 10.

As shown in FIG. 4, outlet valve40 is basically similar to the valve 38except that its valve body 70 is provided with pipe threads 71 at itslower end so that it can be threaded into the closure 40, and theconical seat 72 is at the upper end of the bore 73. The valve member 74is substantially identical with the valve member 60 previously describedand is held in normally closed po sition as shown by a spring 75 thatacts between the lower end of the valve member and a fitting 76 screwedinto the threaded lower end of the bore 73. In operation, when theoperating plate 52 engages the valve stem 46 and depresses the valvemember, the O-ring 77 is moved away from the seat 72 and air can flowthrough the opening in the fitting 76, the central bore of the valvebody 70 around the hexagonal portion of valve member 74 and through theclearance space around the valve stem 46 to the atmosphere.

As noted above, the surge suppressor of the present invention isparticularly adapted for use with airoperated diaphragm type-pumps and atypical arrangement of such a pump and a suppressor made according tothe present invention is shown in FIG. 2. The pump 31 is a well-knowntype of air-operated diaphragm pump and embodies two diaphragm chambers80 and 81. The material being pumped enters through an inlet or suctionport 82 which connects to an inlet manifold 83 leading to both diaphragmchambers and is discharged through an outlet manifold 84 and a dischargepipe 85 that is shown as connected to the conduit 30 to which the surgesuppressor 9 is connected.

The diaphragm chambers are provided with flappertype suction anddischarge valves 86 and 87 and the diaphragms in the two diaphragmchambers are connected together by a rod 88. Compressed air is suppliedto the pump from any convenient source through a hose 89 leading tofitting 90 and the rate of flow of air to the pump is controlled by avalve operated by a handle 91. A valve actuated by movement of the twodiaphragms admits air alternately to the two diaphragms so that thediaphragms are reciprocated in unison, one diaphragm being on thesuction stroke, while the other diaphragm is on the pumping stroke.

Pumps of this type are efficient and long-lived because the diaphragmson the pumping stroke are subjected to substantially equal pressure onboth sides. Since diaphragms and simple flap valves are employed, wearof the moving parts is minimized and it is possible to pump slurries,solutions containing highly abrasive materials and many products thatordinary piston type or centrifugal type pumps are not able to handleefficiently. When the pumps are used in combination with surgesuppressors embodying the present invention, the air supply conduit 39for the surge suppressor preferably is connected to the air supply tothe pump itself, the conduit 39 being connected to the fitting 90 in thepresent embodiment. Thus, the pressure supplied to the surge suppressoris substantially the same as the pressure supplied to the pump.Therefore, the pressure supplied to the suppressor is always adequateproperly to correct the air pressure in the chamber 11 regardless ofwhether the pump is operated at high or low air pressure.

Furthermore, the fact that the pump and the surge suppressor are bothdiaphragm type devices with the material being pumped on one side of thediaphragm and air on the other side in each case, appears to beadvantageous with respect to smoothness of operation and effectivenessof eliminating pulsation from the pump discharge. It is convenient toemploy a suppressor having a diaphragm of the same size and type as thediaphragms of the pump with which the suppressor is to be used so thatthe user needs only to stock one size and type of diaphragm for servicepurposes; however, so long as the suppressor is of adequate size tosufficiently absorb the surges to which it-is subjected withoutrequiring undue movement of the diaphragm, this is not necessary.

The surge suppressor made according to the present invention operateseffectively to reduce pulsations in the discharge of pumps and inparticular in combination with a diaphragm pump, the pulsations arereduced so that they are almost unnoticeable in the discharge piping onthe side of the surge suppressor away from the pump. The operation ofthe suppressor can be observed inasmuch as themovement of the projectingportion 35b of the rod 35 and plate 52 are visible. In operation, whenthe pump is started up with atmospheric pressure in the chamber 10, thedisc 51 contacts the end of the valve stem 45 and opens the inlet valve38 on each stroke until pressure in the chamber has been built upsufficiently to limit the upward stroke of the diaphragm and the disc 51to a point where no contact is made between the disc and the valve stem.As long as condition remain steady, the inlet valve 38 and the outletvalve 40 are operated infrequently, if at all. However, if the pressurein the conduit 30 is increased the disc 51 will contact the valve stem45 for a few strokes, admitting more air to the air chamber 10 andbalancing the discharge pressure; if the pressure in the line 30 isdecreased then the air pressure within the chamber 10 will force thediaphragm downwardly a greater distance and if the pressure is decreasedsufficiently the actuating disc 52 will engage the valve stem 46 forseveral strokes, bleeding air out of the chamber with each stroke untilthe proper balance is again achieved.

From the foregoing, it will be evident that the inventio provides asimple surge suppressor for liquid systems that can be manufactured atreasonable costs and which operates effectively to absorb surges orpulses under varying conditions in the system to which it is attached.In service the absorber requires no attention or adjustment and sinceboth sides of the diaphragm are subjected to substantially equalpressures and the diaphragm is prevented from unduly long strokes, thesuppressor is long-lived in service.

While the suppressor has been illustrated herein in combination with adiaphragm type pump with which it is particularlyeffective, it is to beunderstood that the suppressor is useful in conjunction with pumps ofother types and in other liquid systems that are subjected to pulsationsor surges caused by operation of pumps, valves or the like. In allapplications to which the suppressor is suited, the low rate of buildupof pressure in the air chamber insures effective absorption of pulses.While air has been described as the preferred gas for balancing thepressure of the liquid, under some circumstances it may be desirable touse other gases, for example, nitrogen or another inert gas. It is alsoto be noted that while the surge suppressor is shown in a verticalposition with the air chamber above the liquid chamber, it is possibleto orient the axis of the chamber in any convenient manner since it canbe operated in any position.

I claim:

1. A surge suppressor for liquid system comprising a liquid chamberadapted to be connected to the system and subjected to the pressure ofthe liquid therein, a gas chamber and a movable dividing memberseparating the liquid chamber from the gas chamber, said dividing memberhaving one part subjected to the pressure in the liquid chamber andanother part subjected to the pressure in the gas chamber, the saiddividing member being movable in response to changes in pressure in theliquid chamber, an inlet valve for said gas chamber, said inlet valvebeing connected to a source of gas under pressure and being adapted whenopen to admit gas to said gas chamber, an outlet valve for said gaschamber adapted when open to discharge gas from said gas chamber, andmeans operated by said dividing member for opening said inlet valve andadmitting gas into said gas chamber only during such time as saiddividing member is displaced beyond a predetermined point in onedirection and for opening said outlet valve to permit the discharge ofgas from said gas chamber only during such time as said dividing memberis displaced beyond a predetermined point in the opposite direction.

2. A surge suppressor according to claim 1 wherein the volume of saidgas chamber is several times the volume displaced by said dividingmember in its movement from one of said predetermined points to theother.

3. A surge suppressor for use in connection with fluid conduitscomprising a liquid chamber housing open at one end and providing aliquid chamber, means for connecting the liquid chamber to a liquidsystem subject to surges or pulses, a gas chamber housing open at oneend and providing a gas chamber, a diaphragm clamped between the openends of said housings and separating said liquid chamber from said gaschamber, an inlet valve for said gas chamber, said inlet valve beingconnected to a source of gas under pressure and being adapted when opento admit gas to said gas chamber, an outlet valve for said gas chamberadapted when open to discharge gas from said gas chamber and meansoperated by said diaphragm for opening said inlet valve and admittinggas into said gas chamber only during such time as said diaphragm isdisplaced beyond a predetermined point in one direction and for openingsaid outlet valve to permit the discharge of gas from said gas chamberonly during such time as said diaphragm is displaced beyond apredetermined point in the opposite direction.

4. A surge suppressor according to claim 3 wherein said inlet valve andsaid outlet valve are normally closed and are opened by said operatingmeans.

5. A surge suppressor according to claim 3 wherein said inlet and outletvalves are opened by means including a rod secured to and reciprocatedby said diaphragm.

6. A surge suppressor according to claim 3 wherein the liquid chamberhousing and the gas chamber housing are shaped adjacent the diaphragm toprovide conoidal surfaces to engage the diaphragm and prevent unduedisplacement of the diaphragm in either directron.

7. A surge suppressor according to claim 5 wherein the gas chamber isprovided with a closure member for closing the end of the gas chamberopposite said diaphragm and the inl t and outlet valves are mounted inthe closure member.

8. A surge suppressor according to claim 7 wherein the inlet valve is apoppet valve having a valve stem projecting within the gas chambertoward the diaphragm, said valve being openable by movement of the valvestem away from the diaphragm, said valve having means externally of saidchamber for connection to a supply of compressed gas.

9. A surge suppressor according to claim 8 having an outlet valve alsomounted in said closure member, said outlet valve being a poppet valvehaving a valve stem projecting externally of said gas chamber in adirection away from said diaphragm, said valve being openable bymovement of the valve stem toward the diaphragm, said valve having aport permitting discharge of gas to the exterior of said chamber whensaid valve is opened.

10. A surge suppressor according to claim 9 having an actuating rodattached to said diaphragm and projecting to the exterior of saidchamber, there being means in said closure member to seal againstleakage of air where said actuating rod extends through said pump havingan inlet conduit and a discharge conduit, the pump being connected to asource of compressed air and the liquid chamber of the surge suppressorbeing connected to the discharge conduit of the pump.

12. The combination according to claim 3 wherein the pump and the surgesuppressor are connected to the same source of compressed air.

13. The combination according to claim 12 wherein the diaphragms are ofthe same size and type.

1. A surge suppressor for liquid system comprising a liquid chamberadapted to be connected to the system and subjected to the pressure ofthe liquid therein, a gas chamber and a movable dividing memberseparating the liquid chamber from the gas chamber, said dividing memberhaving one part subjected to the pressure in the liquid chamber andanother part subjected to the pressure in the gas chamber, the saiddividing member being movable in response to changes in pressure in theliquid chamber, an inlet valve for said gas chamber, said inlet valvebeing connected to a source of gas under pressure and being adapted whenopen to admit gas to said gas chamber, an outlet valve for said gaschamber adapted when open to discharge gas from said gas chamber, andmeans operated by said dividing member for opening said inlet valve andadmitting gas into said gas chamber only during such time as saiddividing member is displaced beyond a predetermined point in onedirection and for opening said outlet valve to permit the discharge ofgas from said gas chamber only during such time as said dividing memberis displaced beyond a predetermined point in the opposite direction. 2.A surge suppressor according to claim 1 wherein the volume of said gaschamber is several times the volume displaced by said dividing member inits movement from one of said predetermined points to the other.
 3. Asurge suppressor for use in connection with fluid conduits comprising aliquid chamber housing open at one end and providing a liquid chamber,means for connecting the liquid chamber to a liquid system subject tosurges or pulses, a gas chamber housing open at one end and providing agas chamber, a diaphragm clamped between the open ends of said housingsand separating said liquid chamber from said gas chamber, an inlet valvefor said gas chamber, said inlet valve being connected to a source ofgas under pressure and being adapted when open to admit gas to said gaschamber, an outlet valve for said gas chamber adapted when open todischarge gas from said gas chamber and means operated by said diaphragmfor opening said inlet valve and admitting gas into said gas chamberonly during such time as said diaphragm is displaced beyond apredetermined point in one direction and for opening said outlet valveto permit the discharge of gas from said gas chamber only during suchtime as said diaphragm is displaced beyond a predetermined point in theopposite direction.
 4. A surge suppressor according to claim 3 whereinsaid inlet valve and said outlet valve are normally closed and areopened by said operating means.
 5. A surge suppressor according to claim3 wherein said inlet and outlet valves are opened by means including arod secured to and reciprocated by said diaphragm.
 6. A surge suppressoraccording to claim 3 wherein the liquid chamber housing and the gaschamber housing are shaped adjacent the diaphragm to provide conoidalsurfaces to engage the diaphragm and prevent undue displacement of thediaphragm in either direction.
 7. A surge suppressor according to claim5 wherein the gas chamber is provided with a closure member for closingthe end of the gas chamber opposite said diaphragm and the inl t andoutlet valves are mounted in the closure member.
 8. A surge suppressoraccording to claim 7 wherein the inlet valve is a poppet valve having avalve stem projecting within the gas chamber towArd the diaphragm, saidvalve being openable by movement of the valve stem away from thediaphragm, said valve having means externally of said chamber forconnection to a supply of compressed gas.
 9. A surge suppressoraccording to claim 8 having an outlet valve also mounted in said closuremember, said outlet valve being a poppet valve having a valve stemprojecting externally of said gas chamber in a direction away from saiddiaphragm, said valve being openable by movement of the valve stemtoward the diaphragm, said valve having a port permitting discharge ofgas to the exterior of said chamber when said valve is opened.
 10. Asurge suppressor according to claim 9 having an actuating rod attachedto said diaphragm and projecting to the exterior of said chamber, therebeing means in said closure member to seal against leakage of air wheresaid actuating rod extends through said closure member, said actuatingrod carrying an actuating plate within the air chamber and engageablewith the valve stem of the inlet valve to open the same when thediaphragm moves toward the air chamber more than a predetermined amountand an operating plate disposed on the exterior of said chamber andadapted to engage the valve stem of the discharge valve when thediaphragm moves toward said liquid chamber more than a predeterminedamount.
 11. Apparatus according to claim 3 wherein the liquid systemcomprises an air-operated diaphragm type pump having an inlet conduitand a discharge conduit, the pump being connected to a source ofcompressed air and the liquid chamber of the surge suppressor beingconnected to the discharge conduit of the pump.
 12. The combinationaccording to claim 3 wherein the pump and the surge suppressor areconnected to the same source of compressed air.
 13. The combinationaccording to claim 12 wherein the diaphragms are of the same size andtype.